Method and apparatus for arresting an explosion in a mine



w. B, JAMISON June 2, 1970\ METHOD AND APPARATUS FOR ARRESTING ANEXPLOSION TN A MINE Filed Oct. 25, 123g? 2 Sheets-Sheet l INVENTOR.

WILL B. JAMISON H/S ATTORNEYS June 2, 1970 w, JAMISON 3,515,217

METHOD AND APPARATUS FOR. ARRESTING AN EXPLOSION IN A MINE Filed Oct.23, 1967 2 SheetsSheet 2 INVENTOR.

WILL B. JAM ISON BY I H/S AT TORNEVS United States Patent Office3,515,217 Patented June 2, 1970 Int. 01. A62c 3/00 US. Cl. 169-2 8Claims ABSTRACT OF THE DISCLOSURE Apparatus for arresting an explosionat the mine face and preventing the explosion from propogatingthroughout the mine. A plurality of rigid containers are positionedwithin a mine passageway with the container outlets directed generallytoward the mine face. Each of the containers is provided with a quantityof pulverulent flame extinguishing material and has a frangible discclosing the container outlet. An explosive charge is positioned withineach container in an envelope which also contains a suitable detonatingmechanism. Flame sensing means are provided and are electricallyconnected to the detonating mechanisms in each of the containers. Therigid containers and flame sensing means may be mounted on the miningmachine. When the sensing device is activated by a flame at the mineface, the detonating mechanism explodes the charge in each of thecontainers. The pressure created by the explosion within the container,ruptures the frangible disc and propels the flame extinguishing materialfrom the container through the opening established by rupture of thedisc. The flame extinguishing material is diffused toward the mine faceand quickly extinguishes the flame at its incipiency to prevent thepropagation of the flame and accompanying explosion through the mine.

The method of this invention contemplates providing a rigid extinguisherdischarge container having an explosion detonator and charge, a quantityof extinguishing material and a frangible closure. The method comprisessensing for the presence of a flame within the mine passageway,automatically detonating the explosive charge responsive to the sensingof the presence of flame to rupture the frangible closure and dischargethe extinguisher material through the opening established by the closurerupture.

CROSS REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part of a copending application in part, entitledExplosion Arrestor, Ser. No. 554,212. filed May 27, 1966, now abandonedwhich in turn is a continuation application of Ser. No. 427,227 filedJan. 22, 1965, now abandoned and bearing the same title.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a method and apparatus for arresting an explosion in a mineand more particularly to a method and apparatus for rapidly diffusing aflame extinguishing material to cover a flame shortly after ignition atthe mine face and extinguish the flame before it propagates further.

Description of the prior art In coal mines, explosions have beenclassified as to type of fuel. Generally, the fuel for such explosionsconsists of either a gas, such as methane, or coal dust. While in theadvanced stages of an explosion, both sources of fuel may contribute toburning, in the incipient stages of burning, these two fuel sourcespresent very different problems.

With respect to the flames initiated from coal dust, the fuel is createdby providing sufficient energy to the dust particles to gasify thevolatile constituents in the coal particle. The gas given off the coalparticle in this distillation process is highly combustible. Theignition of this gas creates the burning flame which begins to burn atan accelerated rate as it moves along the mine passageway. Theaccelerated burning establishes increased heating with resultantexpansion of the combustion gas and the explosion is created throughthis accelerated propagation of flame.

It has been found that some protection against coal dust initiatedexplosions may be obtained through the use of rock dust, such aslimestone dust. In using rock dust, it is periodically distributed overthe structural surfaces of the mine passageway, thereby covering thecoal dust particles. Should ignition of the coal dust particles occur atthe face of the mine or at another area of exposed coal dust, the coaldust covered by the rock dust will tend to resist volatilization. Therock dust particles, mixed with the coal dust provide a shielding actionto insulate the coal dust particles from the radiant energy of theburning flame. The coal dust, when admixed or coated with a sufficientamount of rock dust, does not receive suflicient energy because of theshielding effect, to volatilize and the production of additionalcombustible gas is effectively prevented. a

It will be appreciated, however, that there are some obvious limitationsto this means of preventing explosion inducing burning of the volatilematter in coal particles. Coal dust particles are being continuouslycreated by the action of the mining equipment at the working face. Intime, therefore, areas previously adequately coated with rock dust willagain have upon their surfaces, a layer of coal dust particlessubsequently created.

In addition, other areas such as the mine face and the surfaces of coalon the endless belt type conveyor means, as Well as the mining equipmentitself, cannot be conveniently or effectively covered with rock dust. Inspite of the limitations present in the use of rock dust, it does serveas a reasonably effective means of minimizing the possibility of theoccurrence of a mine explosion produced by the burning of the volatileconstituents of coal dust.

A far more serious problem is presented with respect to explosionsinduced by the accelerated burning of methane gas. It is known that anair-methane mixture may be highly flammable and form the basis of anexplosion. Unlike the coal dust fuel source, which requires a relativelyhigh energy source for establishment of volatilization, such as asubstantial electrical spark, the methane-air mixture may be ignited bya low energy source. An abrasion spark, such as that created by cutterbits striking a pyritic particle Within the coal at the mine face maycreate a spark of sufficient energy to provide ignition of themethane-air mixture.

With mechanical mining equipment, it is of course, not feasible toemploy rock dust at the mine face because the machine is continuouslyadvancing and the surface of the face and passageway or entry is beingcontinuously advanced. The machine is of substantially the same size asthe entry so that it is not feasible to continuously disperse rock dustin front of the mining machine. Even if it were possible to disperserock dust in front of the mining machine, this would not eliminate thehazard of a methane gas explosion. Unlike the situation with respect tocoal dust particles wherein coverage with rock dust provides a shieldingaction preventing absorp tion of radiant heat, the methane being gaseousin nature, cannot be encapsulated or effectively shielded from a heat orenergy source. Also, as the methane was created during the formation ofthe coal and is, therefore, contained within void spaces within thecoal, there is no way of accurately predicting the quantity or intensityof methane which will be released from the mine face at any given timeduring the mining operation.

The methane content of the air cannot be effectively controlled byattempting to provide ventilating air at the face of the mine. Themining machine, to effectively dislodge the coal, must be of substantialsize which prevents full exposure to the mine face tothe ventilatingair. Also, as the methane content varies substantially, there would beno effective means of controlling the amount of ventilating airrequired, even if the desired distribution of the air could be obtained.

It will, therefore, be appreciated that in view of the flammabilityhazard created by a methane-air mixture of given concentration coupledwith the lack of predictability of the rate of emergence of methane fromthe mine face, an uncontrollable explosion risk is present in suchmining. As has been stated above, all that is required is that aflammable mixture of methane and air be exposed to a source of energywhich may be relatively low, and burning of the mixture will beinitiated. After the initiation of burning, the heat produced by theburning causes an expansion of the gas and the burning acceleratesrapidly. The speed with which the burning and resultant thermalexpansion of gases increases determines whether or not detonation willresult. Regardless of whether detonation in fact occurs, theaccelerated, uncontrolled burning is considered to be an explosion andmay result in the loss of lives of miners, as well as substantialproperty damage.

Experience in the study of mine explosions has indicated that theinitial increase of velocity of burning of a methaneair mixture occursat a rather slow pace and there is a finite period of time between theinitiation of burning and the existence of what might be called anexplosion. There have been instances where an investigation of a mineexplosion of this type has shown that the mining machine operator,between the time he saw the flame initiate and the time of explosion,had sufficient time to begin to escape and may have progressed 30 to 50feet down the entry from the mining machine before the explosionoccurred.

It will be apparent, therefore, that that there is no effective means ofeliminating the initiation of burning of a flammable methane-air mixtureadjacent the face of the mine. Any attempts at arresting explosion musttherefore be directed toward prompt and effective action taken betweenthe time flaming or burning is initiated and the time the explosionoccurs. If the flame cannot be suppressed or extinguished during thistime interval, an explosion and fire, causing substantial propertydamage and possible loss of lives may occur.

Also, it should be noted that after the methane-air flame has increasedin velocity and accelerated in terms of the amount of heat given off,additional fuel may be such particles of coal dust as are noteffectively shielded by rock dust.

SUMMARY OF THE INVENTION This invention effectively solves the abovementioned problems in the suppression of explosion inducing flames of amethane-air mixture generally occurring at or near the mine face. Rigidcontainers having explosive means and containing pulverulent flameextinguishing material are provided and are operably connected to aflame sensing device in order to explosively discharge the flameextinguishing material responsive to the sensing of a flame. Thesecontainers may, if desired, be mounted upon a mechanical materialdislodging device, such as a mining machine. The responsive explosivedispersement of the flame extinguishing material occurs sufficientlyrapidly that the flame is effectively extinguished before accelerationcan occur. The container is provided with a frangible disc whicheffectively seals the discharge end of the container. The explosion issufficient to rupture the frangible disc and thereby permitsubstantially instantaneous discharge of the flame extinguishingmaterial. The discharge end may conveniently be provided with anapertured end cap through which the material may be dispersed or mayhave a solid end cap adapted to be exlosively removed.

The method of this invention contemplates the sensing for the presenceof flame and the automatic responsive detonation of the explosive chargeto disperse the flame extinguishing material from the container.

It is an object of this invention to provide a method and apparatus foreffectively and promptly extinguishing a flame within a mine passagewayin order to arrest the acceleration thereof and prevent an explosion.

It is another object of this invention to provide a continuous miningmachine having a flame sensing device operatively connected to explosivemeans within a container of pulverulent flame extinguishing material inorder to rapidly disperse said material through an explosion detonatedresponsive to the detection of a flame.

It is another object of this invention to provide a system for theautomatic extinguishing of flames of a burning methane air-mixture byfully automatic means which promptly and effectively disperse a flameextinguishing material over the fire.

It is another object of this invention to provide such a system whereina multiplicity of rigid containers having a supply of pulverulent flameextinguishing material are adapted to be simultaneously dischargedresponsive to detection of flame with the discharge being such as tofully cover the fiamed area with the fire extinguishing material.

Other objects and advantages of the invention will be understood fromthe following description of the invention, on reference to theillustrations appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a top plan view of a borer type of mining machine,schematically illustrated, in a mine passageway and having a type ofsensing device and extinguishing container contemplated by thisinvention.

FIG. 2 is a view similar to FIG. 1 illustrating the mining machine inside elevation with the extinguishing containers discharging the fireextinguishing material therefrom.

FIG. 3 is a schematic elevational view of the mine passagewayillustrating the manner in which the mine face may be covered by thepulverulent flame extinguishing material.

FIG. 4 is a view in side elevation in section of a type of extinguishingcontainer contemplated by this invention.

FIG. 5 is a fragmentary view in section of a modified outlet design forthe extinguishing container.

FIG. 6 is a detailed view in side elevation of a detonator and explosivecharge positioned within the extinguishing container illustrated in FIG.4.

FIG. 7 is a schematic illustration of a mine passageway having a numberof extinguishing containers mounted therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more specifically tothe drawings and more particularly to FIGS. 1 and 2, the mine passageway10 has a roof 12, a floor 14, and ribs or side Walls 16, 18. The miningmachine which has been generally designated by the numeral 20 createsthe passageway 10 in a seam of coal by dislodging the coal from thefront face 22 with rotating boring arms 24, 26. During the miningoperation, the arms 24, 26 dislodge coal from the vertical mine face andthe dislodged coal is conveyed rearwardly on the mining machine by meansof conveyor 28 which moves in the direction indicated by the arrow inFIG. 1. The vertical mine face 22 therefore advances continuouslyinwardly into the mine passageway. The dislodged coal is discharged fromthe conveyor end portion 30 onto a suitable receiving device, such as ashuttle car or the like.

The boring arms 24, 26 have suitable cutter bits 32 that dislodge thecoal from the mine face 22. These cutter bits 32 are illustratedschematically in FIGS. 1 and 2. The boring arms 24, 26 each have a shaft34, 36 which extends into a transmission case 38. Suitable gearing isprovided within transmission case 38 in order to transmit the rotationof electrical motors 40* to the rotor shafts 34, 36. In

the mining machine 20 selected for illustration, there is in addition,an intermediate boring arm 42 which is arranged to dislodge the inwardlyextending kerf of coal 43 as the end boring arms 24, 26 dislodge thecoal from the mine face 22. Finally, drum cutters 44, 46 are alsoconnected to transmission case 38 by shafting 50, 52 so that the drumcutters 44, 46 remove the generally triangular shaped cusps extendingboth downwardly from the roof 12 and upwardly from the floor 14 betweenthe end of rotary boring arms 24 and 26. With this arrangement, agenerally eliptical passageway or entry 10 (FIG. 3) is formed within theseam of coal.

The mining machine 20 has an operators compartment adjacent the rearportion of the mining machine behind the transmission case 38 and theelectric motors 40. Within the operators compartment the operator hassuitable controls 'by which to advance the mining machine into the mineface 22 and dislodge the coal by means of boring arms 24, 26 and 40'.

Secured to the transmission case 38 are a plurality of extinguishingcontainers, generally indicated by the letter B. As is shown in FIGS. 1and 2, some of these are mounted on the top of the transmission case 38,while others are mounted on the side of transmission case 38. Some ofthe extinguishing containers B are generally axially aligned with thelongitudinal central axis of the mining machine 20, while others areaxially oriented at an angle with respect thereto. A flame sensingdevice, generally indicated by S, is also secured to the transmissioncase 38.

Before considering the structure and functioning of these elements indetail, a brief description of their operation might be of value. Whenflame detector S receives an indication of the presence of a flame, itemits a signal to the extinguishing containers B. The extinguishingcontainer has a supply of pulverulent fire extinguishing material andalso has a detonator and explosive charge. The signal from the flamesensing device is communicated to the detonator which is dischargedthereby. The detonation sets off the explosive charge that establishesan explosive pressure and causes the rupture of a frangible closuremember and discharge of the pulverulent flame extinguishing materialfrom the container.

As is shown in FIGS. 1 through 3, the numbering and positioning of theextinguishing containers B are selected so as to substantiallycompletely cover the cross sectional area of the passageway 10 upondischarge thereof. It is seen that extinguishing containers B B B and Bare disposed substantially parallel to the longitudinal central axis ofmining machine 20. Containers B and B are disposed angularly outwardlyaway from the mining machine axis. In FIG. 2, it is seen that containersB and B are disposed generally angularly downwardly, while container Bis disposed substantially horizontally. As is shown in FIG. 3, thedischarge pattern of the pulverulent material substantially completelycovers the generally elliptical passageway 10, thereby insuring aneffective and complete flame barrier.

Considering now the containers B in greater detail, attention isdirected towards the FIGS. 4 through 6. In FIG. 4, it is seen that thecontainer B has a rigid metallic tubular body 60 which is provided witha detonating end 62 and a discharge end 64. The container has a supplyof a pulverulent flame extinguishing material 66. At the discharge endof the container is a frangible disc or closure 68 which effectivelyseals the container interior from the exterior. An end cap 70 havingdischarge apertures 72 is secured to the container body 60 by means ofannular collar 74. At the detonating end of the container body 60, whichin the form illustrated is tapered, is a detonator, which has been shownto be a squib 76. The squib 76 is housed within envelope 78 which alsocontains an explosive charge 80. Envelope 78 is secured to housingmember 82 which is threadedly attached to the detonating end 62 ofcontainer body 60. Lead wires 84, 86 connect squib 76 with flame sensingmeans S. At the bottom of the container B is a mounting bar 88 havingmounting holes 90 through which a suitable fastener may be passed.

Considering the explosive means in greater detail, at-

tention is directed toward FIG. 6. It is seen that envelope.

78 contains an explosive charge 80 and squib 76. Envelope 78 is securedto housing member 82 which is in turn threadedly secured to body member60. The squib 76 is secured to resilient member 92 which in turn issecured within a recess of housing member 82. Lead wires 84, 86 whichconnect the flame sensing means with squib 76 pass through communicatingbores in resilient member 92 and housing member 82.

The frangible disc of closure 68 should preferably be adapted to providea seal against passage of foreign particles and moisture into thecontainer, as well as passage of the extinguishing material out of thecontainer. The disc 68 should preferably be adapted to rupture under theexplosive discharge either into a number of fine particles or with noflying particles to minimize the risk of injury to anyone near by.

In operation, the flame sensing means S which is powered by suitablemeans such as a battery, upon detecting the presence of flame sends asignal by means of lead Wires 84, 86 to squib 76. Squib 76 responsive tosuch signal detonates explosive charge 80 within envelope 78. The shockWave of this explosion causes the frangible disc 68 to rupture, therebypermitting passage of the flame extinguishing material out of thecontainer B. In the form illustrated in FIG. 4, the end cap 70 remainssecured to container body 60 and the material passes outwardly throughthe apertures 72 in end cap 70. The apertures are preferably so placedas to provide the desired high dispersion of the flame extinguishingmaterial 66 so as to insure effective extinguishing of the flame.

In the form of container B shown in FIG. 5, a frangible disc is presentas in the form shown in FIG. 4. The discharge end 102, which is tapered,contains substantially solid end cap 104. With this type of container B,the explosion must fracture the frangible disc and remove the protectivecap thereby establishing a single opening through which the pulverulentflame extinguishing material may pass.

While the container B is being stored, the frangible disc 68, 100 servesa very important function. It provides an effective barrier against theentry of moisture and foreign material such as coal dust, into the flameextinguishing material 66. The entry of such materials into thecontainer B could serve to contaminate and reduce the effectiveness ofthe flame extinguishing material 66. Also, the frangible disc preventsundesired escape of such materials 66 out of the discharge end 64 ofcontainer B prior to a desired use in extinguishing a flame.

As has been stated above, while there is no effective means ofcompletely eliminating the initiation of flame caused by a flammableair-methane mixture, there is a subsequent finite time period withinwhich quick action will extinguish the flame and prevent accelerationthereof tending to lead to an explosion. The apparatus of this inventionis designed to act effectively and quickly within this time interval toarrest the expansion or propagation of such flame. Thus, the instant aflame is detected by sensing device S, a signal is transmitted tocontainer B which causes detonation of squib 76 which in turn sets offexplosive charge 80. The shock Wave from this charge 80, rupturesfrangible disc 68, 100 and simultaneously discharges the pulverulentfire flame extinguishing material to effectively put out the flamebefore acceleration could take place.

The containers B are preferably provided in such number and arepositioned in such fashion that a single signal from the flame sensingdevice will establish simultaneous explosive discharge of the flameextinguishing material from a multiplicity of containers B and therebyeffect complete extinguishing of the flame.

The pulverulent flame extinguishing material 66 may be any suitableparticulate fire flame extinguishing material. It preferably is onewhich may be stored in a container of this sort for an indefinite periodof time without any substantial loss of pulverulent structure. Among thesuitable materials for such use are the alkali metal bicarbonates.Preferred materials for use in the container of this invention includesodium or potassium bicarbonate. Also, if desired, the material selectedmay be protected against water absorption during storage independentlyof the container seal, as by providing a coating of a water resistantmaterial such as silicone, for example.

It is desired not only to limit flame growth in its incipiency at themine face when the passageway is being worked, but it is also essentialto effectively isolate any flaming passageway from any connectedpassageways within the mine. For this reason, as is shown in FIG. 7, itmay be desirable to mount one or more containers B within minepassageways. By so doing, not only will any flames originating withinany mine passageway be restricted to that passageway, but also suchflames may be extinguished prior to an increase in velocity to the pointwhere an explosive detonation may occur. The containers may be mountedon the roof, walls or any convenient place.

The method of this invention, therefore, contemplates providing a rigidsolid particulate extinguisher discharging container having an explosiondetonator and charge, solid particulate extinguishing material and afrangible closure member 68. The method contemplates sensing for thepresence of flame within a mine passageway, automatically detonating theexplosive charge by means of the detonator within said containerresponsive to the sensing of the presence of flame in order to rupturethe frangible closure and discharge the solid particulate extinguishingmaterial through the opening established by the rupture of closure 68.

In the preferred form, the sensing is effected by sensing means mountedon the mining machine and the container is also mounted on the miningmachine. It is also preferred that the sensing be effected continuouslyand automatically, and that the sensor automatically provide a detectionsignal to the container. For more environments, it will be desirable tosimultaneously detonate a multiplicity of containers in order toestablish substantially simultaneous dispersement of the solidparticulate extinguishing material uniformly and completely from allcontainers onto the flamed region.

It will be appreciated, therefore, that the method of this inventiontakes advantage of the relatively slow rate of acceleration or burningof an air-methane mixture. It promptly extinguishes the flame insufficient time to arrest the explosion or propagation of the flame andavoid the substantial risk of injury or loss of life to the miningmachine operator, as well as substantial property damage. This method,therefore, provides an inexpensive means of substantially completelyeliminating the risk of harm from this relatively uncontrollable sourceof explosion creating fire.

8 It will further be appreciated, that this invention provides aneconomical system for extinguishing flame which is adapted for re-use.Once the container, or cannon as it is sometimes referred to, has beenfired, all that is required to place it in condition for further use, isthat it be refilled with the solid particulate flame extinguishingmaterial, the charge and squib be replaced and a frangible disc beinserted.

It will be further noted that the actuation of the extinguishing devicesis accomplished Without the need for any positive action of the part ofthe mining machine operator or other personnel. This is, of course,desirable, in View of the need to act Within a relatively short timeafter ignition of the flame.

It should be understood that any suitable flame sensing devise that isoperable to sense the presence of a flame, transmit a signal to thedetonator to actuate the detonator may be used with the previouslydescribed invention.

I claim: 1. A method of arresting explosions in a mine adjacent the mineface by directionally propelling extinguishing material into andextinguishing a flame comprising mounting a rigid extinguisher having adischarge opening on :a mobile machine positioned adjacent the mineface, said mobile machine arranged to advance with the mine face duringthe mining operation,

directing said discharge opening of said extinguisher toward said mineface, mounting a flame sensing device on said mobile machine, saidsensing device being operable to sense the presence of a flame in thevicinity of the mine face,

connecting said flame sensing device to said extinguisher so that saidflame sensing device, upon sensing a flame, actuates said extinguisher,and

said extinguisher upon actuation dispersing an extinguishing materialthrough said discharge opening in a preselected direction toward saidmine face and into said flame, and

extinguishing said flame.

2. A method of arresting explosions in a mine adjacent the mine face bydirectionally propelling extinguishing material into and extinguishing aflame as set forth in claim 1 in which said extinguisher comprises arigid nonfrangible container having a discharge opening, said containerhaving a quantity of solid particulate extinguishing material thereinand pressure generating means to propel said particulate materialthrough said discharge opening,

said flame sensing device, upon sensing a flame, actuating said pressuregenerating means and propelling said particulate material through saiddischarge opening and dispersing said particulate extinguishing materialinto said flame and extinguishing said flame.

3. A method of arresting explosions in a mine adjacent the mine face bydirectionally propelling extinguishing material into and extinguishing aflame as set forth in claim 1 which includes a plurality ofextinguishers mounted on said machine,

said extinguishers each includes a rigid nonfrangible container having adischarge opening, a detonator, an explosive charge, a quantity of solidparticulate extinguishing material and a frangible closure for saiddischarge opening,

said flame sensing device, upon sensing a flame, detonating saidexplosive detonator in said extinguisher, said detonator detonating saidexplosive charge and rupturing said frangible closure and propellingsaid particulate extinguishing material through said discharge openingsand dispersing said particulate extinguishing material into said flameand extinguishing said flame.

4. A method of arresting explosions in a mine adjacent the mine face bydirectionally propelling extinguishing material into and extinguishing aflame as set forth in claim 1 which includes:

mounting said plurality of extinguishers and said flame sensing deviceon a continuous mining machine adjacent the material dislodgingelements, and

continuously operating said flame sensing device during the operation ofsaid mining machine.

5. A method of arresting explosions in a mine adjacent the mine face bydirectionally propelling extinguishing material into and extinguishing aflame as set forth in claim 3 which includes substantiallysimultaneously detonating said detonators in said plurality ofextinguishers when said sensing device senses a flame.

6. In apparatus for arresting mine explosions,

flame sensing means adapted to detect the presence of flame within amine passageway, rigid container means having a rigid nonfrangibleelongated generally tubular metallic container housing a flameextinguishing material said container means positioned adjacent to saidflame sensing means,

explosive means within said container means to substantiallyinstantaneously discharge said flame extinguishing material from saidcontainer means being responsive to detection of a flame by said flamesensing means,

said metallic container having a discharge end provided with a frangibleclosure and an end cap, said container having a detonating end providedwith said explosive means,

said explosive means having a squib connected by electrically conductivemeans with said flame sensing means, and

said squib disposed Within an elongated tubular envelope containing anexplosive material and adapted to detonate said explosive materialresponsive to detection of a flame by said flame sensing means.

7. In apparatus for arresting mine explosions as set forth in claim 6wherein,

a multiplicity of said containers are secured to a mining machine insuch position that said discharge ends of said containers are directedgenerally toward said mine face when said machine is in use,

said flame sensing means so positioned on said mining machine to detecta flame originating in the immediate vicinity of the mine face, and

each said squib operatively adapted to detonate said explosive materialresponsive to a signal indicating detection of a flame in the vicinityof said mine face by said flame sensing means and thereby substantiallysimultaneously produce explosive discharge of said flame extinguishingmaterial toward said mine face from all said containers.

8. In apparatus for arresting mine explosions as set forth in claim 7wherein said flame extinguishing material is a solid pulverulentmaterial.

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